In wireless communication systems, wireless service providers may operate radio access networks (RANs), each RAN including a number of base stations radiating to provide coverage in which to serve user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices. In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a UE within coverage of the RAN may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other UEs served by the base station.
Further, a RAN may operate in accordance with a particular air interface protocol, examples of which include, without limitation, Orthogonal Frequency Division Multiple Access (OFDMA (e.g., Long Term Evolution (LTE) and Wireless Interoperability for Microwave Access (WiMAX)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), Global System for Mobile Communications (GSM), IEEE 802.11 (WIFI), BLUETOOTH, and others. Each protocol may define its own procedures for registration of UEs, initiation of communications, handover between base station coverage areas, and other functions.
In accordance with the air interface protocol, each base station may provide wireless service to UEs on one or more carrier frequencies (carriers), each of which could be frequency division duplex (FDD), defining separate frequency channels for downlink and uplink communication, or time division duplex (TDD), defining a frequency channel multiplexed over time between downlink and uplink use. Each carrier or its respective channels could be within a defined frequency band and could be of a particular frequency bandwidth, such as 5 MHz, 10 MHz, or 20 MHz for instance, defining a certain extent of air interface resources. A given base station could be arranged to serve a UE on a single such carrier at a time or, with carrier aggregation service or the like, on multiple such carriers at a time.
Further, each base station in such a RAN may be communicatively linked with a signaling controller that carries out various network control functions, such as managing setup of bearer connections between the base station and one or more transport networks, tracking where UEs are located in the RAN, paging UEs, and the like. In addition, neighboring base stations may be communicatively linked with each other, to facilitate handover and other inter-base station signaling.
By way of example, in an LTE RAN, each base station (LTE evolved Node-B (eNodeB)) has a communication interface with a signaling controller known as a mobility management entity (MME), the base station and MME each also have a respective communication interface with a gateway system that provides connectivity with a packet-switched transport network, and the base station has a communication interface with each of its neighboring base stations. Typically, the nodes of such an LTE RAN would sit on a wireless service provider's core packet-switched network (e.g., a network compliant with the industry standard system architecture evolution (SAE) for the LTE protocol), and so the base station and each other RAN entity (e.g., MME, gateway, and neighboring base station) may each have an assigned Internet Protocol (IP) address on that network, and the interfaces between these entities may be defined as logical connections (e.g., established virtual tunnels) through that network.
In example operation, when a UE enters into coverage of an LTE base station on a particular carrier, the UE signals to the base station to initiate an attach process and to establish a radio-link-layer connection with the base station. In this process, the base station signals to the MME, the MME authenticates the UE, the MME and base station obtain and store a context/profile record for the UE, and the gateway system assigns an IP address to the UE for use by the UE to communicate on the packet-switched transport network. Further, at this point or later, the MME may engage in signaling with the base station and the gateway system to establish for the UE one or more bearers for carrying packet data between the UE and the transport network.
Once a UE is attached with a base station, the base station then serves the UE on one or more carriers, managing downlink communication of packet data to the UE and uplink communication of packet data from the UE. For example, as the gateway system receives packet data destined to the UE, the gateway system may forward the packet data to the base station, and the base station may schedule and provide transmission of that data to the UE on the UE's serving carrier(s). Likewise, as the UE has packet data to transmit on the transport network, the UE may transmit a scheduling request to the base station, the base station may schedule transmission of that data from the UE on the UE's serving carrier(s), the UE may accordingly transmit the data to the base station, and the base station may then forward the data to the gateway system for output on the transport network.
In practice, the base stations of the RAN may not always provide seamless coverage throughout an area, and therefore a wireless service provider may implement many small-cell base stations throughout the area to help fill in gaps of coverage. To connect such a base station with the network infrastructure in such a situation, the wireless service provider may implement a wireless backhaul interface (also referred to as a “wireless backhaul connection”) between the base station and another base station of the service provider's RAN. In this situation, the base station at issue operates as a relay base station, and the other base station operates as a donor base station. In practice, the relay base station includes or is coupled (e.g., via a local area network or other connection) with a UE, referred to as a relay-UE, and the donor base station then serves the relay-UE in much the same way that the donor base station serves other UEs. Further, the relay base station itself serves UEs, in much the same way that any base station would.
With this arrangement, when the relay-UE attaches with the donor base station, the relay-UE may acquire connectivity and an IP address as discussed above for instance. But based on a profile record for the relay-UE, the RAN (e.g., a signaling controller) may recognize that the relay-UE is a relay-UE (rather than a conventional end-user UE) and may therefore set up a bearer connection for that relay-UE with a special core network gateway system (also referred to as a “relay gateway”) that provides for internal core network connectivity and assigns the relay-UE with an IP address for use to communicate within the core network. Once the relay-UE receives that core network IP address assignment, the relay-UE may then convey that IP address to the relay base station for use by the relay base station as the relay base station's IP address on the core network. The relay base station may then operate as a full-fledged base station of the RAN, having IP-based interfaces with other core network entities (e.g., a signaling controller, a gateway system, and other base stations), albeit with those interfaces passing via the wireless backhaul interface provided by the relay-UE and via the relay gateway.
Once the relay base station is thus in operation, the relay base station may then serve UEs in the same way as a standard base station serves UEs. Thus, when a UE enters into coverage of the relay base station, the UE may signal to the relay base station to initiate an attach process, the UE may acquire an IP address, and an MME may engage in signaling to establish one or more bearers between the UE and a gateway system. Each of these bearers, though, like the relay base station's signaling communication, would pass via the relay's wireless backhaul interface.